The present invention relates to the preparation of dihydroxydiphenyl alkanes by the reaction of phenol and dihaloakanes. More particularly, it relates to an improved catalyst for the preparation of 4,4'-dihydroxydiphenylethane sometimes referred to as bisphenol E.
Dihydroxydiphenyl alkanes, also known as bisphenols, are useful in the production of high polymers, epoxy resins and high-molecular weight thermoplastic condensates as well as intermediates in organic syntheses, the best known of such compounds, bisphenol A, being widely employed. It has been suggested in an article by I. M. Nosalevich et al entitled "Preparation of dihydroxydiphenylalkanes by the alkylation of phenol by dihaloalkanes" [Vestn. Khar'kov. Politekh. Inst. 1971, No 60, 61-4 (Ukrain)] that an increase in the number of technically available dihydroxydiphenyl alkanes would open up possibilities for modification of polymeric materials formed from them. Following this line, these workers have described several methods of preparing dihydroxydiphenyl alkanes among which is that of the direct interaction of phenol with dichloroethane or dibromoethane in the presence of zinc to give the 1,2-bis(4-hydroxyphenyl) ethane (also known as 4,4'-dihydroxydiphenylethane) and its isomers. Zinc-containing compounds such as the salts of zinc and particularly the halides of this metal as well as zinc oxide have been found to catalyze the reaction. It has now been discovered, however, that a combination of certain zinc-containing compounds is a more effective catalyst for this reaction and provides advantages which cannot be achieved with either of the zinc compounds used separately. It is an object of the present invention, therefore, to provide an improved catalytic process for the production of dihydroxydiphenyl alkanes using zinc-containing catalysts. It is a further object of this invention to provide a process for producing dihydroxydiphenyl alkanes from phenol and a dihaloethane wherein reaction rates are increased and the induction period observed with catalysts such as ZnO for example, is substantially eliminated. Further objects and advantages of the invention will become apparent from the following description and the appended claims.